Christian anger over threats in Iraq

If you have seen a trending Facebook profile photo that looks like a smiley face in the past few days, look again.

It's probably the letter N written in Arabic, which is being used to mark the homes of Christians in Iraq who were told to pay, convert, leave or die at the weekend.

The ultimatum has sparked a worldwide social media protest.

Facebook profile pictures of the symbol, short for Nasara or Nazarene, are rapidly being uploaded across Australia after militants drove hundreds of Iraqi Christian families out of their homes in Mosul.

The city has been emptied of Christians for the first time in its history.

"There's a 9/11 that's been happening every single day," said Andrew Kozah, who changed his profile photo to raise awareness.

"No one really cares about Christians being persecuted. World leaders barely acknowledge what's happening to them.